The medial nasal processes form the two primary palatal processes that protrude medially; they are initially separated by a furrow (incisura interglobularis). They merge and form the primary palate (primary nasal floor). In adults, the primary palate corresponds to the premaxillary part of the hard palate (premaxilla) which lies anterior to the incisive foramen and posterior to the upper incisors.
At S18, the upper lip arises below the nostrils. The lateral parts of the upper lip originate from the maxillary process, which fuses together with the lateral nasal process. There are different opinions about the origin of the material for the medial part (philtrum). According to one theory, it comes from the globular process of the medial nasal prominences; another theory argues that its innervation by the maxillary nerve proves that it originated from the maxillary prominence.